1. Field of the Invention
The present invention relates to a sensor equipped wheel support bearing assembly having a load sensor built therein for detecting a load imposed on a bearing unit for a vehicle wheel.
2. Description of the Related Art
For safety travel of an automotive vehicle, the wheel support bearing assembly has been well known, in which sensors for detecting the respective rotation speeds of the vehicle wheels are employed. While the automobile traveling safety precaution is generally taken by detecting the rotational speed of the respective vehicle wheel in various locations, it is not sufficient with only the rotational speed of the vehicle wheel and, therefore, it is desired to achieve a control for safety purpose with the use of other sensor signals.
In view of the above, it may be contemplated to achieve the vehicle stability control based on a load acting on each of the vehicle wheels during travel of an automotive vehicle. By way of example, a large load acts on the outside wheels during the cornering, on the wheels on one side during the run along horizontally inclined road surfaces or on the front wheels during the braking, and, thus, uneven load acts on the vehicle wheels. Also, even in the case of the uneven live load, the loads acting on those wheels tend to become uneven. For this reason, if the loads acting on the wheels can be detected as needed, suspension systems for the vehicle wheels can be controlled beforehand based on results of detection of the loads so that the stability control of the automotive vehicle during the traveling thereof (for example, prevention of a rolling motion during the cornering, prevention of diving of the front wheels during the braking, and prevention of diving of the vehicle wheels brought about by an uneven distribution of live loads) can be accomplished. However, it is difficult to find a suitable space for installation of the load sensor for detecting the load acting on the respective vehicle wheel and, therefore, the stability control through the detection of the load is hardly realized.
Also, in the event in the near future the steer-by-wire is introduced and the system in which the wheel axle and the steering come not to be coupled mechanically with each other is increasingly used, transmission of information on the road surface to the steering wheel, then hold by a driver, by detecting a wheel axis direction load would come to be required.
In order to meet those needs hitherto recognized, a wheel support bearing assembly has been suggested, in which a strain gauge is affixed to an outer ring of the wheel support bearing assembly so that strains occurring in the outer ring can be detected when the rolling elements pass through. (See, for example, the Patent Documents 1 listed below.) Also, the wheel support bearing assembly has been suggested, in which a sensor device including not a strain gauge attached directly to an outer ring, but a load sensor for detecting strains attached to a sensor support member. (See, for example, the Patent Document 2 listed below.) In the case of the Patent Document 2 referred to, the sensor support member is made up of a horizontal portion, held in engagement with an outer peripheral surface of an outer ring, and a vertical portion held in engagement with a vehicle body fitting flange of the outer ring, with the load sensor attached to the horizontal portion.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2003-530565    [Patent Document 2] Japanese Laid-open Patent Publication No. 2006-077807    [Patent Document 3] JP Patent Application No. 2006-062252    [Patent Document 4] JP Patent Application No. 2006-228906